ChangeLog.d/new-mbedtls_x509_crt_parse_der_with_ext_cb_routine.txt

Features
   * Add new mbedtls_x509_crt_parse_der_with_ext_cb() routine which allows
     parsing unsupported certificate extensions via user provided callback.
     Contributed by Nicola Di Lieto <nicola.dilieto@gmail.com> in #3243 as
     a solution to #3241.